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. 

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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.