That is not eczema.
I have never seen eczema in my life in a hamster and I have had them over 40 years.
I think you should stop using the cream right away and return to the vets or see another vet. The ham may well have had a reaction to unsuitable cream. If it licks the cream it will do it no good either. Vets do not normally give cream to hams for this reason.
I think that this is an abcess. It may need draining, flushing and then treated with antibiotics (definitely needs antibiotics) They should give you Baytril (0.1ml by syringe into the mouth once or sometimes twice a day). (don't accept 'put it in the water' as they do not get the right dose.)
If it does not clear with Baytril or at least improve in a week then there is a chance that this is in fact a tumour which has started to break down on the skin surface. Can you feel any firm lumps in the area. An isolated tumour like this can be removed but it is quite a large lesion and would need a few stitches. Still worth a go though in a younger hammy. We have had a few lumps removed with good results.
Get the Baytril asap. Phone the vet and say your hamster has gotten much worse on the cream. Ask about an abcess? It is important to keep an abcess open and draining till the pus has stopped coming out so it does look bad but it heals from the inside out.
Keep the cage very clean to try and avoid infection.
Wish I'd seem the pic last night