Bathroom sink has no water..

Hello,
First time posting.
I'm looking around online to see if anyone can give me some advice.

My living room half bath sink was dripping recently.
Its a delta model with wide spread type.

So I looked up online and saw it could be fixed by cartridge replacement.
dripping was happening from cold side so I bought the replacement part from home depot.

Followed youtube videos, peoples postings.
So first I turned water valve off.
Got the handle off, replaced the cartridge and now theres no water coming out!!
Even the hot side doesn't work now... I literally only opened the cold water handle to replace the cartridge!

I first suspected the cartridge but that didn't explain why the hot side suddenly stopped working as well.
Now I unscrewed the bolt to check just in case the water stopped flowing while leaving the valve on..
but suddenly water was spreading out everywhere as soon as I loosen the bolt.. (made a huge mess..)

I just don't understand.. any idea whats going on?
In summary.. only replaced a cartridge on cold side handle.. suddenly water stopped entirely.
When loosen the bolt of cold side handle water pumps out but when I put everything back together it doesn't work again..

Please help..
I don't know if I messed up the whole thing..
Just fyi, all other bathrooms are fine..

 

awesome!!!!
That was such a simple fix.. I just bought a new aerator for 5$ in home depot and got it replaced.. now water comes out !!
Cannot thank you enough