On the right side of my head/neck, just at the hairline, I have had a firm bump for a couple months. Have had mono twice. Have night sweats.?

# of possibilites. The firm bump could be a lymph node, a sebaceous cyst, an acne cyst, among others. The area described sounds like part of the lymph node chain called posterior cervical. If you had mono recently, it may be from that and slowly should resolve. The area drains infections from several areas of face and scalp on that side. Night sweats makes me think infection. 2 months? Go for check-up & blood tests.