Re: Crack sound in the lowest part of my biceps?
I would say go see a physio. It could be a simple matter of tight tendons, requiring maybe some simple massage and regular stretches to sort, but could also be far more serious.
I woul recommend physio rather than doctor, as this is their speciality. I trusted a minor injuries doctors with pain in my shoulder, and three of them failed to identify a dislocation. I know it was because movement in my sleep put it back and the pain of it woke me up. Wish I'd gone to a proper physio.
Regular stretches are a good way of avoiding a lot of injuries, and the area most people, especially males tend to omit.
'If you think you can, or if you think you can't, you're probably right.' Henry Ford