Bump on left upper arm, numbness in left arm numbness started about 3 weeks and bump been fodidnt notice a while,didnt notice i thought i bumped it, its is slightly tender when touching it ?

Examination: Is required - may be a bruise with surrounding nerve inflammation or may be some sort of nerve problem such as radiculopathy (pinched nerve) with a concurrent lump. Could also be a shoulder injury with associated nerve irritation. A doctor examination will help sort through this and then if necessary tests can be run if the diagnosis still remains unclear. All the best.