ive owned/had family pets all of my life. we've always taken our pets to the vet at the first signs of illness or discomfort (its been easier with dogs, obviously). gizmo has been my first pet just by myself. his first injury was a tooth infection from a fall, then a broken tooth, and just recently a URI. i would never "self vet" any of those, mostly because i have no idea how. when Giz recently had his URI, i contemplated using left-over baytril from his tooth infection. but without knowing the proper dosages, or if there was anything else to be done, i didnt take those chances.
personally, i would probably be ok with taken care of cuts and scrapes (minor surface ones), but thats honestly about it. in terms of dry/small poops, i'd probably do a bit of massaging, a bit of run time to see if it gets the gut moving, but more than a day of that, i would take to the vet. in my eyes, if something is going on INSIDE the body...and i cant see it, then i want an experienced vet to take a look. i think large breeders have a better ability to self treat, mostly cuz they know (at least should know) the species inside and out and know what to look for.
granted, chinchilla injuries are not like something we'd need Dr. House for, but going to the vet to get a proper diagnosis seems the most sensible to me. i was about 95% sure giz was getting a URI. and i had the Baytril in my fridge. but i know that if something worse developed, id be upset with myself.