Everybody has done it. OK, not everybody, but you're in good company. I have a 3/16" flush rivet in one of my fuel tanks because of a mistake like that.
Depending on how close it is to other holes, you can simply drill it out to a nice round hole, then countersink it or dimple it and set a rivet in the hole.
Epoxy would be OK too (as would something like JB weld), but you still need to clean up the hole.
Do a search on the site for "Extra dimple" or other likely phrases. You'll get some ideas.