The only thing written on Element Attunement is what is on PHB p.81. The term "nearby" has no official game definition, so regualar usage rules apply, and the DM makes a call if something is too far away to be nearby.
Senisible limits might be set at any of the following, with reasons a a DM might choose them:
- 5 feet, as it is adjacent to you on a grid system.
- 10 feet, as that is a reasonable distance to be to a candle or torch you might need to light, or food you want to cook/cool.
- Line of sight, you can't know it is nearby or aim it, if you can't see it.
This class feature is similar to Druid Craft, Thamalorgy (I'll fix the spelling in an edit), and Prestidigitation, in that that it isn't a combat feature but a utility/role play feature. I would assume the vauge range is a product of either: it being a utility or RP effect where moving to use it doesn't typically affect action economies, the clever usages already require the DM to make a call on weather the use is legit, or they just got lazy on this one :) . Regardless of why, no there is nothing more specific.