Tamaris I had this problem as my job was a huge part of my life, not just the work itself but also the social side of things. I'm also constrained by medical problems.
My main hobby since I retired, is researching my family tree. I also tend to do certain things to keep busy, which I didn't have time for when I was working. I set time aside for pampering myself, like doing my nails, looking after my hair, and looking for bargains for clothing and shoes. I have friends round for lunch, and in turn I visit them.
I read a lot, do crosswords, and have taken up knitting again, and sometimes I bake for local church fetes etc. I do tend to steer clear of daytime TV which I consider dire.
There are days when I don't actually speak to anyone but this doesn't bother me one jot.
Also, if you can drive, get out and about to appreciate local geography and history. There's also nothing wrong with going to the theatre or cinema by yourself.