Horrible rotten milk smell coming from kitchen, no idea where it is coming from

A few days before I went to parents for Christmas I did spill some milk but wiped it up instantly, thats what the smell is like i.e strong smell of rotten milk, I smelled inside the fridge and its fine, in the cupboard below sink and its fine, just this horrible smell coming from somewhere.

I mopped up last night with boiling hot soapy water under the fridge and this morning smell is still there so tried again today and also used disinfectant and the smell is still there.

No idea where the smell could be then.