The length of an erection can vary, and under normal circumstances an extended erection should not lead to permanent damage.
Diseases like sickle cell anemia can lead to priapism, which is a dangerous side effect.
Imaging the penis for structural damage and blood flow can be considered if the symptoms continue. I would also consider blood tests to evaluate for any hormonal problems.
These options can be discussed with your personal physician.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
kevinmd_