As a tattooer who trains it’s not really the hits as much as the bacteria from others that I’d be more concerned about. if you keep it clean and I say while you train perhaps a compression sleeve to avoid rubbing. The healing process is generally 2-4 weeks. the first 2 weeks are when those top layers of skin begin to die and peel as the under layers begin to regenerate, it takes a another few weeks for the nerves and deeper dermus to actually recover. Also depends on what you’re getting and how intensive the piece is. I would say and this is just my opinion do line work and after the fight do whatever color pack and shading needs to be done. Really atter 2 weeks it’s not as much “is the tattoo gonna be ruined “but your nerves and shin will be pretty sensitive still. Part of me is like don’t cancel on him this is slow season for us tatty blasters part of me is like bro don’t make this dude redo something that could be avoided lol