Suggest Remedy For Beginning Of Bed Sore In A Person With Dementia And Parkinsons

My Dad is 93 with Advanced dementia and Parkinson Gait so does not walk that much of course. He has what I thought was the beginning of a bed sore which has not opened. It is located about an inch in his crack down from his tailbone. Abouth the size of a nickle and is slightly hard and painful for him while sitting which is all he does. I have been lathering with dermacloud ointment (fanny cream) for lack of knowing what to do for about 3 days. He is so feeble it and too cold to get out so do you have any suggestions. Thank you in advance!