First, I'd be concerned that there may be further damage. Since the valve spring closes the valve, the valve and piston may have come in contact.

Possibly the spring itself just failed. Hard to tell without replacing the broken spring and checking.

Does the valve move smoothly in the guide? That should indicate whether the stem is bent.

Fit a new spring and test compression again to see if the valve still seats correctly. If compression is good you should be OK.

If problems show in the checks above the head will have to be pulled.

Hope it's OK for you.