Hard bump above vagina

I just noticed hard bump above my dogs vagina because I saw her sitting on the snow up and down.

I forgot to post a picture and breed. She is half golden Retriever and half  Chow Chow. 

Hello!  It looks as though there may be thickening of the perineal skin here, although it is difficult to tell why.  I wonder about things like scraping the delicate region against the floor, or biting the skin.  This could happen for a variety of reasons including anal gland disease, parasites, allergy, infection, season / cycle changes or abnormalities, hypothyroidism, pressure at the skin fold etc.  A check by the vet may be in order to rule some of these possibilities out / instigate or provide treatment as necessary.