Lump in my right armpit, no redness and tender only when it is touched/ pushed on Immovable, been there 3 weeks. Ultrasound showed no fluid in it??

Not a cyst. is all that means. More information about what the ultrasound saw to be more informative. In the axilla lymph nodes are usually present. So more information about what the ultrasound showed is needed before I can give you more complete answer.