Collagen injections??

[columbo]

Hello all, I had a cystic acne as a kid, took accutane which got rid of it but the cysts left depressions in my chin. I was wondering if there is any health risk that anyone knows of in getting collagen injections or perhaps something more permanent like some of the foam inplants ive seen advertised on the web? If anyone here has any experience with these injections, i would appreciate your point of view and if i decide to have the procedure done, does anyone know how one goes about finding a credible doctor? Ive heard some cosmetic horror stories i'de like to avoid.