Knee and elbow pain since last two days, mild headache, joint pain, is this arthritis ?

Uncertain: Sometimes there can be joint inflammation with infections but it sounds like your symptoms are mild.

Varies: Osteoarthritis is a degenerative condition and so the symptoms of pain are usually much more chronic than you are describing. Some patients can develop a reactive arthritis in which joints can become painful and swollen and this can sometimes be associated with a viral infection . This would seem more likely with what you are describing. I would not hesitate to see a primary care doctor.