SQL Server 2012 - How to view the locks' log?
If you haven't already turned on the blocked process report, then it's not possible to jump back in time to view past blocked processes.

However, I find that where there's blocking, these two already-on things help:

First, SQL Server tracks which indexes are involved in blocking. It doesn't tell you which queries are involved, nor is it permanently reliable (the data disappears at odd times), but it's a start. You can query sys.dm_db_index_operational_stats to learn more, or use the open source sp_BlitzIndex to see it. sp_BlitzIndex identifies the indexes involved in blocking as "Aggressive Indexes" - that can be a little confusing, so here's a post on how to interpret those warnings.

Second, if there's blocking, there's sometimes also deadlocking. And good news! SQL Server tracks deadlocks by default in the system health session, and you can indeed query those with the open source sp_BlitzLock. It doesn't hurt to give that a shot - it may identify which queries are causing you problems.

(Disclaimer: I wrote some code in those open source procs, and I wrote the blog post referenced in here.)