It sounds like you are experiencing some weakness in the muscles of the hand that affect your pinch grip. These are the same muscles (flexor pollicis longus of the thumb and flexor digitorum profundus of the index finger) that make it possible to form the “OK” sign.
An examination by a medical doctor would be a good place to start to find out what’s going on. You may have a temporary nerve dsyfunction. The most likely nerve involved is the anterior interosseous nerve. Anterior interosseous nerve (AIN) palsy is fairly uncommon. But what we do know about it suggests some unknown cause for a malfunction that seems to correct itself over time.
There may be a nerve entrapment from scar tissue, connective tissue, or other fibrotic tissue pressing on the nerve. The lining around the nerve called the nerve sheath may be affected. But the fact that in most cases, the nerve seems to recover suggests more than just pressure on the nerve from tight tissues around it.
Treatment is usually just a wait-and-see approach. The average amount of time required for nerve healing is about 12 months from the start of your symptoms. But before making any assumptions, get an accurate diagnosis and recommendations for treatment based on that.