What to do when android phone is stolen?

[Neveen]

My phone was stolen from me today (i'm sure its not lost cause it was taken away from me) and i didnt have any security apps or so for this kind of thing. I'm really worried about the thief getting to my personal stuff/ or even logging into my accs (how creepy is that). How can i stop him from that? if i change a password for facebook for example, will it still let him get on my acc through the phone? or what else can i do?? i heard its possible to erase all phone data but i guess thats impossible if i didnt have an app installed for it beforehand? if it matters at all ik that he removed the sim card (cant phone anymore).

id be super thankful for any answers!!
ill go to my provider or whatever that's called and get them to close it off or what not hope it works. thanks again everyone!