See a physician. You should seek medical assessment/treatment. If there is new-onset pain a doctor needs to urgently assess your risk for having a significant underlying problem (e.g. Blood clot) and, if necessary, send you for an ultrasound. Varicose veins are often chronically symptomatic. If acutely so (esp if inflamed), an ultrasound should be performed to see if it is phlebitis vs phlebitis + occult deep clot.
Depends. Varicose veins can hurt, so pain related to them can be expected. But other vascular causes can also cause pain, such as claudication from poor blood flow and blood clots. Where the pain is, what kind of pain, and various other history and physical exam findings can help clarify the cause.