Weird skin lumps....dr says reaction to "something" but still there after weeks...

[Badders123]

Just that really
After our hols in North Yorkshire (so nowhere exotic!) ds2 came out in lumps on his elbows.
Dr said reaction and advised hydrocortisone which we have been using since.
Except they seem to be getting worse...
Wwyd?
Go back?
Keep on with the cream?
No idea what they are.
Doesn't look like excema to me (Dh and ds1 both have that) it's lumpy and white.
Pic but below but not a great one.

It's only on his elbows btw.
Nowhere else.

Oh and if it's relevant he was dx with vitiligo last year