### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
I have had a knot on my right side at the top of my ribcage for years. This morning when I woke up, the knot and the area around it are sore. No physical activity yesterday that could have caused a muscle injury. The area is warm to the touch but not hot. It dully aches unless touched and then it feels like pain from a bruise. It seems swollen but the swelling is not visible. I had the knot looked at about five years ago and ultrasound doctor said it was nothing. The position is more towards the back versus being close to my breast. I m 30. And my menstrual cycle ended 3 days ago. The knot is mobile and I am able to move it between my fingers. It doesn t seem any larger than it was five years ago. It is hard but not like a bone or marble.

### output:

Hi! Thanks for writing to Chat Doctor sharing your health problem! In short, swelling means collection, pain means infection/irritation and mobile means benign... Therefore, your lump on the rib cage is not a thing for worries but still it should be cured because of possible complications like infection, severe pain and morbidity. I must recommend a needle biopsy first to confirm the nature of the lump and as per my experience, it could be:1. Lipoma/neurofibroma like benign skin lesions2. Inclusion cyst like sebaceous cyst3. Lymph node enlarged due to local infection even tuberculosis etc.4. Ectopic breast tissue/tumor like fibroadenoma or fibrotic disease Hope you got the answer; please revert to us if any more clarification IR required! Wishing you good health.