What to do if i have allergy like symptoms which causes right eye pain and right side headache. is it related to brain tumor?

Not likely: The allergy symptoms may lead to sinus infections/swelling. This, in turn can lead to the right sided headaches. Brain tumor usually lead to local effects on the brain such as weakness if the tumor is close to the motor areas. Headaches are late findings, and may occurr if the tumor is very large.

Dry eyes?: You need to see an ophthalmologist asap to make sure that you don't have glaucoma which can cause permanent blindness if not treatment in time. Dry eye is yet another cause for your symptoms. Rush and don't just walk and tell your eye doctor that it is an emergency. Allergy may cause headaches but not right eye pain.

Could be: I would say this could be tumor, but there is something called cluster headache which occurs more in males than females and can cause red eye and nasal congestion with the headache on one side. However, I would like to ask you if this headache occurs in patterns and how long have you had it? I recommend that you have your headache checked to rule out tumor as well.