My fresh pea soup came out too watery. What can I do to save it? Or can I use it for a sauce or something?

How about heating it slightly to reduce it further while making a roux-- flour cooked into butter-- and adding the roux as a thickener?

Can you place about half of the soup in the blender to cream up the consistency?

You could also try reducing it a little more, keeping it at a low simmer for a while. If you want to make it creamier or change the texture without trying that, you could add plain yoghurt or similar to thicken it up.

Let it sit for at least 24 hours in the fridge. The extra liquid will, most likely, rise to the top. Pour it off and save it to use in a vegetable stock (add it toward the end of cooking, or to dilute a reduced stock). ;o)