I have a lump on my neck and if i clench my teeth my neck muscles expand and the lump is more prominent, what could it be?

Could be: Could be inflamed lymph node from tooth or gum infection, thyroglossal duct cyst, benign or malignant lesion, and so many other problems. Any pain, bleeding, and/or (as in your case) swelling should be immediately investigated. Please call your Dentist, an Oral Surgeon, or an ENT Specislist for a differential diagnosis, and, if necessary, treatment.

See your physician. : The lump that you have discovered on your neck could be many things. I would think it could be a common cyst under the skin and above the muscle so that it would show more when you contract these muscles. It is always better to know so if serious it can be treated promptly and usually with better prognosis. Good luck.

Suspicious lump?: Regardless the cause... I would advise you to have the lumps on your neck examined by a primary care specialist (e.g. ENT, OFP). Any suspicious lump that does not resolve itself in 2-3 weeks should be evaluated.