I'm 19 yr old healthy male,but yesterday my classmate hit very hard on my back on thoracic spine, i feel slight muscle pain on either side.any danger?

Contusion on back: You likely sustained a contusion to your back. This is a form of bruising to the skin and underlying muscle. This will likely heal after a week or so. If your pain persists or moves beyond where you were hit, see a doctor.

If the pain is on: the side of your spine, it is most likely muscular. You should watch for increasing pain, any weakness, numbness or tingling. If you have any of those, you should see your doctor or go to the emergency room. If the pain continues, you should also be examined. If you have no medical contraindication, you can try ibuprofen for the pain.