Due to the swelling and dark mass above the injury I think she/he has either a big splinter in there, or a broken toe that's got a messy break to it.
I would bathe the wound in something disinfectant, even saline or iodine solution, and see if there is a foreign body in there; whether there is or isn't, Stockholm tar (pine tar) would help if you have it. Stockholm tar pulls splinters out even if they're below all layers of skin and in the muscle, and it kills even gangrene and golden staph. It's also a potent painkiller and can stop the pain in a second or two. It promotes rapid and often scarless healing.
It should heal up ok but may be painful for quite a while. But please make sure you don't let it get infected.