Welcome! I am Dr. Altman, a licensed veterinarian and happy to answer your questions today.
I am so sorry that Oscar has this new growth. The primary concern is something like a sty since it is not troubling Oscar but with his age it could potentially be something more concerning such as a tumor
I definitely would not advise continuing the vaseline at this point which can be an irritant to the eye. You can use a saline flush for contact lenses to flush the eye and the cloth to wipe it clean. In addition putting a moist towel in the freezer for 30 minutes then applying it can help with the irritation
Lastly benadryl at 1 mg/ pound every 8 hours will help with the redness and irritation but it might cause mild sedation initially.
I would advise taking a photo tonight of the area with a coin or ruler next to the lump to monitor size and if it is still present on Monday or is growing then please have your veterinarian evaluate the area to ensure medical intervention is not required. Sometimes these lumps can rub the cornea and cause a corneal ulceration
which can be terribly painful but if it is not improving your vet might want to prescribe a topical medication to quiet down the irritation and possibly shrink the lump
Please let me know if you have any additional questions I can assist with today!
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