This is a huge opportunity! Do restrict access to resources. After all, what is an adventure RPG without obstacles to overcome? This is a golden opportunity to have natural, sensible obstacles that can be overcome with a variety of creative methods, and which will drive your players to more fully engage with your world.
So, the town has lost access to its regular trade routes. The townspeople will simply be forced to adapt, either abandoning their resource-starved professions or finding new sources of needed materials. The smith can't smith because they've run out of their reserve of ingots? No more metal weapons for the PCs... until they find a new source of iron ingots.
The PCs walk into the potion shop, and see the shop owner has her arm in a bloody sling.
"Oh! Sorry, I'm closed. Closed for good, woe is me! I've run out of herbs and powders and I've sold my last potion. I guess I'll have to go work on the new farm Mayor Colby has been organising. I tried to get to the Fungus Caverns to gather things to experiment with, but the way is long and there were monsters. Monsters! If only the way was safe, I'm sure I could gather some things that I could use to brew with again..."
The caverns are wild and dangerous, and the PCs are the only ones who can change that. Give them obvious hooks, backed up by a need (a lack of available stuff to buy), and let them figure out how to solve the problem and "unlock" a town feature they will want for the future.
🔒 Town Smithy
Yury the Smith has run out of iron bars and can't make any new items. Locate a new source of refined iron to unlock the Town Smithy.
(Yes, that's slightly videogame-y, but it's a tried and true formula for a reason. And done via natural PC-NPC interactions, it doesn't have that videogame feel.)
Do the PCs try to broker a trade deal with the deep gnome city they recently discovered? Do they try to sneak in and steal a supply of iron? Do they instead recruit townspeople to set up a mine to exploit the iron veins they found across the underground river, despite the goblin tribe nearby? Do they hire the goblins to work the mine?! Will they set up a smelting operation in town, or will they sell the ore to the deep gnomes in exchange for a percentage of the resulting ingots? Will they just let the smith turn to farming since they've found a neutral kobold town where they can buy basic gear? Or will they do something absolutely unexpected and give the GM that rare opportunity to be surprised by their own campaign?
Each of these is a potential adventure all on its own, and that's only from one unmet need.
Not only that, each of these is a failable mission, which is a rare and valuable beast to a GM, when so often GMs are advised to fudge rolls and use smoke-and-mirrors tricks because "the PCs have to win every encounter, otherwise the campaign ends." Since the success or failure of any of these solutions to the iron supply crisis merely means they'll have to try a different way, you can afford to make success contingent on the PCs' actual skill and players' actual cunning rather than just hand them pre-made success. Having real power to affect the world restores a lot of agency and investment to the players that is often casually denied to them. If they try to broker a trade deal with the svirfneblin and cock it up by going murderhobo on a gnome who annoys them, then they get the chance to experience a meaningful outcome of their actions, and they'll just have to find some other way of supplying the town with iron. And when they succeed, it is a very real victory that they'll savour.
All that, just from one unmet need. When you consider how many needs a town has – food, water, metals, reagents, cloth, building materials, fuel (different types for different needs, since you can't forge with oil and you can't light a house with coal), salt (and other methods of preservation), and others I'm sure I'm forgetting – you've got an immense number of ready-made adventuring motives, all for free! Just add a need and a reason that need isn't being met, and you've got an instant reason for the PCs to go exploring new parts of the cave system.