A trigger finger or thumb is when your finger or thumb feels like it catches or locks and then is difficult to straighten.
After a period of time and some pain, it then releases, gives way and straightens. It is due to a thickening or swelling of your tendon that gets caught as the tendon passes under its pulley or sheath. It can be from arthritis or overuse of the tendon. It usually occurs at the A1 pulley of the flexor tendons at your knuckle joint or at the MCPJ of your thumb.
You will need to wear a splint that blocks the movement of the finger for a minimum three weeks, or in some cases up to ten weeks. If there is a lot of swelling you may require an isotoner glove or coban to reduce swelling.
Try to change your movement initially while grasping objects. If there is absolutely no change after three weeks, you may require an injection or possibly surgery.