There seems to be no obvious/visible fracture. The tiny bone is a sesamoid bone which is normal. There could be an injury to the tiny ligaments in the thumb which could be the cause of pain. If you are able to Fold and extend the finger with pain, it rules out tendon injuries.
Next Steps
Apply ice, do not Massage, take Anti inflammatory tablets and Apply Thumb Spica
Health Tips
Do no apply hot water, it will only increase the swelling. Give rest to the thumb