retention cyst

I just had a mri done on my cervical spine do to a work related accident. I had a big sheet of plaster fall on my head. Since the incident I have been having bad headaches and neck pain. The doc explained it as a whiplash injury and prescribed therapy.
After I left his office I noticed on the report the following.

"A mucus retention cyst is noted in the sphenoid sinus which appears mildly hyperpneumatized" can you anybody tell me what is means? I left a message but it takes for ever to get a call back,

[Paderla Anitha, DNB]

Hello and hope you are doing well.

Sorry to hear about the accident. The sphenoid sinus is a cavity located in the sphenoid bone. And infection or inflammation of this sinus can cause a mucous retention cyst. It is not related to the accident. Check with your doctor to rule out sinusitis.

Hope this helped and do keep us posted.