My left vagina lip is extremely swollen hard and sore, it really hurts i've also got a fever and feel quite unwell . what is it?

Herpes?: Lumps, bumps, blisters and other skin abnormalities on the genitals need to be evaluated. An examination will be needed to know the cause and treatment. You may be describing a herpes infection. This can present this way and cause fever and flu like symptoms on the first outbreak.

Get evaluated ASAP: Your symptoms are concerning enough that you need to be evaluated by your physician immediately.

An infection: You are likely suffering from an infection. Should seek the help of a doctor in the next 24 hours. Ideally seeing an ob/gyn would be of benefit as you may need to have an incision of this sore.