I have a tumor in my left distal femur that has caused a hairline fracture last year. I have been feeling pressure and pain. Should I be concerned?

Osteonecrosis. Yes! be concerned. The tumor you had was probably a benign non-ossyfying fibroma. Usually, if your growth plate has closed (you've stop growing), then the bone growth won't exceed your bodies ability toget rid of the dying bone so that it won't cause problems. When you continue to grow osteonecrosis (dead bone) can remain and cause pain, or the the tumor can recur. Both require an mri- immediately.