Most bruises do spread a bit, or appear to grow, but you should see a change in colour in a few days indicating that it is dissipating. If you were 'leaking', you'd see suppuration or actual blood...there'd be no doubt for you. But the blood vessel comprises a lot of endothelial tissue which is rapid-healing.
Just don't rub the incision when you shower!! Not for about six days, or whatever your leaflet says.