My left wrist pain doesnt go away after a month. Dont remb any trauma to it. Only hurts (sharp pain)when I bend my hand backwards/supp weight wif palm?

Wrist sprain. Sounds as though you likely have a wrist sprain. Although fractures initially, if minor trauma, may look benign in nature and the swelling and bruising may develop over the following hours. Something to keep an eye on and if worsens quickly, see your local doctor.
See details. There are several possible causes with tendinitis being a common one. It is impossible to offer specifics without being able to examine the wrist. See an orthopedist or rheumatologist.