There is an app called Anti-Social that promises this; but the reviews are all 1 star.
The next best place to look would be the various ad blocking apps. However none of the ones I saw mention blocking social network widgets. It might be worth researching (or contacting the developers of these apps) to be sure.
It’s hard to say if it’s possible in iOS. While the methods to block social widgets should be similar to ad blocking, it’s probably enough different to cause issues. The main complaint about Anti-Social app is that it blocks too much of the sites, making them unusable.