What do i do with tomatoes boiled with the skins on

Peel them.

If you blanch tomatoes for a minute you can peel skins. After that you can continue to cook and break them down to make tomato sauce or even ketchup.

After boiling cool and remove skin, then crush  saute olive oil and garlic  and onions if u like add tomatoes cook 30 min or more add salt and pepper now u have a fresh tomatoes sauce for pasta , parma dishes, or what ever u like u can add fish to the sauce or whatever 

The skin will crack if you dip tomatoes in boiling water, so it is easy to peel off.  Incidentally you can freeze tomatoes and when you want to cook it, just dip the frozen tomatoes in warm water the skin just peels off easily.