I Have 3 Small 'dot Like' Bruises On My Triceps

i have 3 small 'dot like' bruises on my triceps arm area (left arm). I don't think it is due to heavy lifting as I don't recall of lifting anything as well as I haven't fallen over. it is unexplained and I'm in a lot of pain and it is tender when touched and when my arm is stretching or moving.