Hello I am Dr Ravinder Sharma ENT surgeon
On the basis of information provided it appears that you have collection of pus or mucus in one of your sinuses. Possible cause is chronic sinusitis
. However there can be other causes too like - If you have any history of trauma it could be fluid covering the brain tissue. I would advise you for a ENT consultation and a CT scan
of Paranasal sinuses
to decide on further line of management.
I hope this answers your concerns. Feel free to contact me if your need more information on this
With warm regards