First of all sorry to hear that you have been dealing with sinusitis, and now have a cholesteatoma. Not sure if they are necessarily related, but I can give you some information on cholesteatoma. In order to understand how a cholesteatoma forms, you must first understand some normal anatomy in the ear. The outer ear canal is lined with keratinizing squamous cell carcinoma (similar to the skin that covers your body) up to the tympanic membrane (ear drum). The middle ear is the space that is internal to the tympanic membrane, and is lined with mucosa (different then keratinizing squamous cells).
If there is a violation in the tympanic membrane for any reason, and some of the keratinizing squamous cells get into the middle ear space (this can also happen from a retraction pocket). Once the squamous cells get into the middle ear, they can grow and build-up keratin debris. This collection of squamous cells and keratin debris is what is typically thought of as a cholesteatoma. The problem is that they are expansile, and if left to expand for long enough can erode through crucial middle ear structures. thus they need to be removed.
The only way that this can be related to your history of sinusitis is if the nasal swelling has led to obstruction of your eustachian tube which led to a vacuum in your middle ear creating a retraction pocket in your ear drum and resulting in a cholesteatoma. I would definitely recommend following up with an ENT. Hope this helps.