Injured hand. looking palm side r hand, bruise at base of outer part of thumb & outer bottom palm part of hand. can move thumb. could it be ligament?

Sprain: There are quite a few ligaments and tendons around the base of the thumb and joints of the hand therefore any injury to this area can easily result in a sprain or rupture of these ligaments. If it's not causing much discomfort and you have full normal strength there is no need for concern as most sprains settle down in a week or two. You may need further imaging and workup if symptoms persist

Bruising: Indicates injury and bleeding under the skin that's what the bruises Are so anything that causes a little bit of bleeding can cause bruising it could be a ligament or tendon a the bone just some capillaries or can be something called a bruise which is just basically local irritation from impact or trauma