Is it possible to get bruises from working too hard...?

Too long didnt read will be at bottom.

Recently, my right arm has started to hurt. I'm not sure what the term for it is, but on the side that would show if I held my hand out to recieve something? Then the area inbetween my hand and elbow. My arm will feel kinda weird around there often, it kinda like pulses. It doesnt feel too good. But its not like extremely painful, or painful enough to stop me from working. So I figured I'll just ignore it, it'll go away. My job requires a lot of heavy lifting. I work as a busboy at a pretty nice restaurant. I work on the far side of the restaurant thats away from the kitchen, and we have bins we put plates in instead of running every single plate to the kitchen. By the time its time for me to take it it probably weighs about 50-60 pounds. I run it to the kitchen which I think would be maybe about 70-100 feet? Im usually the one that takes it every half hour or so because they hired this kid that just doesnt take initiative very often at all, so I constantly run it back there. I also try stacking up as much plates as I can before I take them to the bin. It puts a lot of pressure on my fingers and support from my arms. I'd say most weight I've carried in plates on one hand would be about 10-15 pounds. At the end of the night we have to bring chairs and tables in we have for outside. Again that kid has to help me but he moves so slow I just dont count on him. I'll stack up 3-4 chairs at once then carry them inside. Each weighs about 15-20 pounds. I'm not strong at all, I'm not athletic, I dont work out much. Ive been trying to start working out again, but my right arm has been kinda losing strength because of this. I can do more curls with my left than my right. Today while working I looked down at my arm and noticed 2 bruises in the area thats been pulsing a bit and kinda hurting. I havent hit my arm on anything, as far as I can remember. Is it possible to bruise from doing a lot of physical work?

TL,DR; My job requires lots of heavy lifting. Lower arm started hurting. Havent hit it on anything lately. Now I have two bruises in area it was hurting.