Ask an Eye Doctor and Get an Answer ASAP
Can you attach the photos here? Pain or itch? How old are you? Are you a male or female? How tall are you? How much do you weigh? When did it start? Any other symptoms? Are you aware of anything which might have triggered it? Any medical problem? Any surgeries? Any medications including over-the-counter pills? Any family medical history?
It could be herpes, a conjuctival cyst, or allergic reaction. You should see an eye doctor to have exam.