bulbul, your son is eating cream not because he likes it but just because of curiosity. Another important thing is that at this age kids tend to do whatever they are asked not to do. Now the best way for you is that either just explain him when he gets hold of the cream or just keep it away from his visibility.
I am sure if he eats a lot of this it could harm him.

My daughter is used to eat Vaseline. Mostly she is used to putting every other thing in mouth. But I think she likes Vaseline. I keep it away from her and am trying to explain her slowly. But as of now she does not listen to me at all.

I think a toddler just enjoys different experiences. It may be in breaking things, taking things in mouth etc. etc. Putting things in mouth they may be getting to experience different tastes.

I have 3 kids and each of them have been through this phase. My youngest one was used to eating his crayons. And it was something which I had to give him to color. I stopped this habit of his by just showing him how well he could color with it and also as he enjoyed coloring if he took the crayons in mouth I would not give him the crayons for a whole day.

bulbul, similarly maybe you can let your son know how the cream is used for keeping his skin smooth & healthy. Also if he repeats his behavior just don't put any cream on that day and you use cream for yourself in front of him. This may help.