My weak arm become blue after a workout

[7Maxz]

I was doing some biceps curl as i can with my weakest arm so i can improve my strength and biceps, but when i work out with it, it became blue/purple, it was not painful, my skin color came back after 2 mins, but that was the first time i had this, is it bad ? I don't think it's a bruise

[SuffolkPunch]

Probably is pooling blood - that's basically what a pump is.

As long as it doesn't hurt or lose sensation, you are probably fine. Adapting to lifting does involve some odd pains and niggles at times.