Inch deep laceration on wrist with no pain, what to do?

Seek care: Inch deep laceration of the wrist would put tendons and median nerve at high risk for injury. Nerve laceration may be why pain perception is altered. Seek care with a qualified hand surgeon.

Medical treatment is: indicated. Go now. May need stitches if wound depth > 1/4”, wound edges are gaping or jagged or if fat / muscle is visibly extending from wound. If you can’t stop bleeding that requires medical intervention.See: http://www.mayoclinic.org/first-aid/first-aid-cuts/basics/art-20056711

Sounds like a: cut or laceration with a good bit of luck. Cuts over the wrist can injure tendons, nerves and lead to infection. If a cut is not painful that doesn't mean that a deeper injury can't have taken place, an exam of nerve and tends of the fingers and wrist is needed so that an injury can be addressed