Allergic Reaction: This could be due to an allergic response to chlorine or other chemicals in the swimming pool, leading to eyelid swelling, and potentially causing headache and body pains due to the systemic release of histamines.

Infectious Conjunctivitis: Swimming in contaminated water can lead to conjunctivitis, which might cause eyelid swelling. If the infection is viral, it could also lead to systemic symptoms like headache and body pains.
Irritant Conjunctivitis: Exposure to chlorine or other irritants in the pool can cause conjunctivitis, leading to eyelid swelling and discomfort, possibly accompanied by headache.
Sinusitis: Swimming can force water into the sinuses, leading to infection or irritation, which might cause headache, facial pain, and potentially eyelid swelling if the sinuses around the eyes are affected.

Meningitis: Although rare, if the swimming water was contaminated with certain pathogens (e.g., Naegleria fowleri), it could lead to meningitis, which presents with severe headache, fever, and potentially body pains. Early diagnosis is crucial.
Cerebral Venous Sinus Thrombosis: This is a rare condition that could be triggered by dehydration or other factors related to swimming and could present with headache and possibly body pains, but it's critical to diagnose due to its high morbidity and mortality.

Trichinellosis: If the swimming water was contaminated with Trichinella larvae (highly unlikely in a typical swimming pool setting), it could lead to trichinellosis, which might cause eyelid swelling (due to facial edema), headache, and body pains among other symptoms.
Leptospirosis: Swimming in water contaminated with the urine of infected animals could lead to leptospirosis, which can cause a wide range of symptoms including headache, body pains, and potentially eyelid swelling due to conjunctival suffusion.