Turtles do get infected ears so it could be that. It could also be a botfly larvae. I suggest taking the turtle to a vet, turtle person, or wildlife rehabilitator for treatment either way. There are Midland and Western painted turtles too which may be native to CO. Are you sure it's an Eastern painted turtle? I suggest finding out for sure the species and what to do. In the mean time, you can take care of him. My page on turtles is at
http://www.fishpondinfo.com/turtles/index.htm and has general information. My turtle (an Eastern redbellied turtle) is a lot of work. Since you have to do water changes, they're more work than box turtles.
Good luck!