What if you hit your shin and it hurt but it didn't bruise. a week later though there was a hard lump on my shin. could i have chipped my shin?

Hematoma: If there was no bruise, the trauma was probably more blunt which can still cause some blood oozing into the skin, forming a hematoma in a few days. If it ellicits sharp pain on pressing on it, you may need to get an X Ray to rule out a chip fracture. In the meantime, Ice, immobilize with an Ace bandage, and take ibuprofen to help it heal soon. Feel better:)

Could be: You may developed bleeding under the lining, periosteum, of the shin. Leave it alone, just observe it. If it does not grow, it will resolve though it may take a few months. If it grows, becomes red and painful, see a doctor.