Be not afraid; pursue fun
You need to discuss this with your group first.
I'm quite concerned that this may impact our game very negatively. Personally, my character shuns gold and does not possess a value over treasure, but there are several members of our group who are completely driven by it. I'm scared what could possibly be done with this much gold, as I am fairly new to D&D and I don't quite know what is available to those with heavy coin purses.
- The group can still have fun with this even if your PC is an ascetic. The aggregate experience is the key.
- You might (as a group) screw up: so what? Failure and screw ups can lead to hilarious and memorable fun. (We play games to have fun, mostly).
- If you aren't discrete about your pile of loot, adventure will come to you. Parties of freebooters, pirates, bandits, and other unsavory sorts (like adventurers) may come after your ill gotten gains, filthy lucre, treasure horde, etc. You'll be able, with some planning, to reduce the number of murder-hobos in your game world by simply letting them come to you and taking them out, or by bringing them to justice. (And you'll have the dough to rig/bribe any jury or judge, just to make sure. wicked grin )
- You may get a visit from Smaug, or your world's equivalent. Dragons love gold. The lore of the book The Hobbit includes the "why" of Smaug coming to Erebor and taking down the dwarves and men of Dale: naked greed. He heard rumor of their wealth and fame, and decided to come and make it his. (Start hiring scouts and archers, eh?)
- You are being given a chance to explore a question millions of people have: if I won the lottery, what would I do with all of that money?
You won the lottery, so you now get to role play the answer to that question.
Studies have been done on lottery winners, which found that quite a few have blown their winnings and been back where they were to start with within a year or so of winning. Your objective? Don't be that guy! Make something with this windfall rather than blowing it on (whatever).
Decide as a group
From your comment/amplification, 4 out of 6 are worried that this is too much gold - the DM being one of them, as he didn't foresee the use of a portable hole in that trap room. You don't have to keep it if your collective brainstorming session within the group on what to do with it gets overwhelmed by the order of magnitude involved. Find a cave, dump most of it or all of it down a deep hole, and let fate take care of the rest. Spread rumors of cursed gold if you like.
But if you choose to keep it, or most of it ...
The number of mundane things you can purchase with that much gold is impressive: ships, small castles, iron mines, gold mines, wagons to start a caravan business, horse flesh of the highest quality, raising an army to accomplish (mission X). The list is bounded only by your imagination. These are but a few things to start investigating which might also lead to further adventure.
Example:
"Hey, someone hijacked our silk shipment last week. Let's get after them and get it back, and see which crime lord (or commercial rival) is behind it!"
Your DM is inducting you into a time tested mode of play that I am very familiar with, called
"Give 'em enough rope!"
The operating theory is that, as a DM, you give your players enough rope to play with. They'll either hang themselves or make a hammock with it. Either way it can result in some memorable fun.
Bottom Line: what you do with this is Have Fun with this new pile of loot.
Coda: for the DM
Since the DM didn't figure out how you'd get past his treasure room trap, the DM can easily rule/retcon that 99% of it is actually iron pyrite aka fools' gold. This is a reasonable retcon, based on how the gold was collected. The player with the mage hand didn't see through the illusion in the room that made all of the gold look like the real stuff: the DM intended this to be a trap room, right? The players will find out that when they try to spend it that "your money is no good here" is a common response. Savvy merchants notice that the coins are not real gold. Alternately, all of it is copper with the thinnest of gold veneer/plate, which was meant to lure the greedy and unwary ...