If you have fingers missing on one hand but you are still able to punch can you still be a pro boxer?

No reason why not. It is not a requirement of any boxing commission that the boxer have all their digits to fight. Of course it would be limiting the boxer to some effect as they would have a slightly less force of impact (the bit of reduced weight) but I see no reason why that would be too much of a problem. More important would be an increase of injury to the hand missing the fingers as it would be tougher on the "fingerless knuckles" at impact. If you can hit a heavy bag with the same full force as with the undamaged hand and you suffer no injury then I'd say go for it.

HOW MANY DIGITS ARE YOU TALKING? IS IT MORE SENSITIVE THAT YOUR OTHER HAND? I COULD GIVE YOU A BETTER ANSWER. RODHOOK

John Elliott who was silver medallist in the Middle Weight division of the 1924 Olympics( on a doubtful points decision) and went on to a successful professional career in England, the US and Australia was missing a thumb as the result of an accident on a Naval Ship at the end of WW1.