Osteoarthritis: This is a common condition that can cause pain and swelling in the fingers, including the tip of the ring finger. The lack of signs of infection or trauma makes osteoarthritis a plausible explanation, as it is often related to wear and tear over time.

Gout: Although more commonly associated with the big toe, gout can affect any joint, including those in the fingers. It causes sudden, severe pain and swelling, which could fit the symptoms described.
Rheumatoid Arthritis: An autoimmune disorder that can cause pain, swelling, and stiffness in the joints, including the fingers. It might not be as common in a single finger but could be part of a larger pattern.
Tendinitis or Tenosynovitis: Inflammation of the tendons or their surrounding sheaths can cause pain and swelling, especially if the ring finger has been subject to repetitive strain or overuse.

Ganglion Cyst: Although often painless, a ganglion cyst can cause discomfort and should be considered, especially if there's a noticeable lump.
Referred Pain from the Neck or Shoulder: Sometimes, pain in the fingers can be referred from issues in the neck or shoulder, such as a herniated disk or thoracic outlet syndrome. Missing these diagnoses could lead to prolonged suffering and potential neurological damage.
Raynaud's Phenomenon: This condition affects blood flow to the fingers and toes, and can cause pain, swelling, and discoloration in response to cold or stress. It's crucial to identify as it can be associated with underlying autoimmune diseases.

Sarcoidosis: A condition that can cause inflammation in various parts of the body, including the joints, leading to pain and swelling.
Psoriatic Arthritis: An autoimmune condition that occurs in some people with psoriasis, causing joint pain, swelling, and stiffness.
Tumor (Benign or Malignant): Although rare, tumors can cause localized pain and swelling. A thorough examination and possibly imaging studies would be necessary to rule out this possibility.