Hey! I'm really sorry to hear about your injuries. As a standard basis, every guitar player need to build strength and dexterity when they start so in theory, all the standard exercise should be good however, there's your injury that come into play and unless someone else here went through something similar, I feel like a doctor specialized in injury recovery would be better at guiding you since yours is a particular case.
Don't know if you knew but Tony Iommi, guitarist of black sabbath, also lost the tip of his middle and ring finger by accident. That didn't stop him to become one of the greatest guitar player of all time so don't discourage and I hope you find something that works!