Get browser extensions like StayFocusd or LeechBlock
Put every damn social media site you've ever heard of in the block list... In fact, go out of your way to find ones you haven't even heard of and put them in there too.
Put any other site in there that distracts you
Set that thing to block ALL DAY
Phone notifications OFF, put phone down UPSIDE DOWN on table.
Enjoy a day of productivity and concentration. :)
Other tips:
Does music help you? If so, plug in.
How about tea or coffee? They help me.
How about moving to an area where you can be less distracted by people?