Harmonica or penny whistle are good places to start.
Accomplished jazz guitarist Django Reinhardt could not use his ring or little finger on his left hand after a fire in the caravan he lived in and he was a world class guitarist.
You could probably play many aspects of the guitar if you were shown the usual way and adapted the technique as Django did. You could probably hold a plectrum in the other hand to pluck the strings with. That would not be easy, but might be something to work towards should you find that you like the harmonica etc.
Many accomplished musicians have overcome a hurdle to reach their goal.
How is your singing? Don't forget your voice is an instrument or do you fancy the drums. (do you have full use of both legs for bass drum and hi-hat?)
I would suggest that the harmonica may be the best place to start as you can make progress quite raoidly and it takes little investment initially (about �6.00 each. they come in different keys). You can play along with most things if you have the keys of A, C, D,G.
Whatever you choose, remember it is meant to be fun so enjoy it.