This might sound stupid, but check with your Dr first to be sure there isn't something else going on. Diabetics can NOT go to nail places. Diabetes plays a role in your feet for discoloration and nail changes. There are other underlying medical conditions that can play a role in your feet changes too.
Be safe first. Then, by all means, try suggestions, pedicures, etc.
I use a foot exfoliator cream and srubby to keep my feet callous free and rough skin to a minimum. I'm a barefoot person, so it's a chore sometimes.
Good luck!