Complaining about a sore bum all the time?

So my LG has started constantly complaining about a sore bum and she pulls at her nappy. She generally doesn’t like nappy changes or sudocrem but has started asking for nappy changes and sometimes even wants the sudocrem. Her skin looks fine, no redness or spots, so I’m at a loss at what’s going on. I suspect she might be referring to her vagina and not her bum (I’ve not taught her that word yet). I’m not sure if I should be taking her to a doctor? I can’t see anything that could be causing pain and I don’t know what to tell a doctor other than she says she’s sore. Anyone know of any invisible things that might be causing her pain? I’ve googled but it’s been unhelpful