Will my hands be able to stretch fully after a badly bruised knuckles? no broken bones. healing over 2 weeks. no discoloration but still sensitive.

Strain or contusion: If you had X-rays done and there were no fractures, or broken bones, and, if you are able to close (flex) your fingers and open them (extend) some, then this means that you probably don't have any permanent damage. Time will tell. Injuries like this can take 8 to 12 weeks to heal fully. When in doubt, if not improving soon, you need to see an orthopedic doctor.