the symptoms u have described point to a local infection which may also be present in urinary tract
. these can be related to irritation by tight clothings/moisture/excessive activity e.g. walking/ other mechanical irritation. rarely diabetes
may be there (but at ur age its less likely). Infections of urinary tract are common in girls and enlarged finger nails can worsen them in case u scratch it often. Drink plenty of fluids, keep dry, use cotton clothes, apply a bit petoleum jelly (vaseline) before passing urine it will make a barrier and avoid burning sensation. oral antibiotics
may be necessary for few days, consult a local doctor for that. don't get afraid from reporting to doctor but be afraid of consequences if it worsens. be bold and relax.