Ive had an immovable small(?) lump on middle of neck since aug. its longish and at the top end its round if that makes sense. dull pain in that area when i yawn/burp/swallow sometimes. i got blood tests and they said it was fine. what could it be?

Blood tests alone may not be enough and US or CT of the neck may be indicated. However, if the lump does not evolve (change in shape and size) in 4 months the lesion, if present, is likely benign.

What did your physician think the lump was? Thyroid nodule? Cyst? Lymph node? A blood test is not sufficient for a diagnosis. If you're not satisfied, consult an otolaryngologist (ENT specialist) for evaluation and advice.