Hello Jester123 If the eye is white and clear, there is no discharge and the vision is good the eye itself is probably not the problem. Ther are two things that are common that might cause this: first an early stye or eyelid infection. Usually there is a place on the eyelid that is painful and tender to touch. Second if the lid is swollen but not tender or red it may mean that there is an allergic reaction involving the eyelid. Often its something that was inadvertently rubbed on the lids such as chemicals, plant herbicides, insecticides, solvents, ink, facial cosmetics, hair coloring, etc. The list is endless.
Home treatment is probably limited to warm or cool compresses. If Benadryl over the counter doesn't make you sleepy you could try that. Fallback is to see an ophthalmologist tomorrow if you're no better.
JCH III MD Ophthalmologist Eye MD