I was lifting weights and suddenly I felt pain in my biceps. I stopped my exercise and applied ice immediately. Today I've noticed lump on my muscle. There is also mild pain. What happened? Did I tear my muscle?
It's just a muscle contusion. The lump you see is just a hematoma. You probably weren't warmed up enough. Just apply cold pressure on it, and if it doesn't heal in few days visit your doctor.
I forgot to add. You should use the RICE formula:
Rest: Protect the injured area from further harm by stopping play. You may also use a protective device (i.e., crutches, sling).
Ice: Apply ice wrapped in a clean cloth. (Remove ice after 20 minutes.)
Compression: Lightly wrap the injured area in a soft bandage or ace wrap.
Elevation: Raise it to a level above the heart.