Will a finger with a hairline fracture be swollen and numb for long?

Yes: Your hands, feet, and face have a lot of sensory nerves and sensory representation on the brain. Any injury to these areas will be more noticeable for a longer period of time than injuries to other areas.

No: Should heal in a few weeks. Most fractures even with slight displacement heal in 6 -8 weeks. Non displaced, hairline-not bad should heal faster.