This is a known issue with the EF 50mm f/1.4. The most common cause of the problem is that the guide slots at the end of the focus collar inside the lens have become bent. The most likely cause for the bent collar is an impact to the lens, such as being dropped, when the focus is set to a short distance.
Sometimes turning the manual focus ring very fast will push the focus mechanism past the 'sticking point' and allow you to get to shorter or longer focus distances. A quick twist of the focus ring provides more force than the micro-USM motor inside the lens does.
Always storing your EF 50mm f/1.4 with the focus set to infinity will help protect your lens from this problem if it experiences a sudden impact. The screws that retain the plastic guides inside the slots on the helical collar can also work loose and cause similar focusing problems. The exact same dis-assembly/assembly procedure is required to get to either problem to repair them.
There are some online resources that show you how to repair the lens yourself. Do so at your own risk, but it is not too difficult a repair as far as lenses go and if you have an aptitude for working on small mechanical devices and can follow long, detailed instructions carefully you can probably pull it off.
Repairing AF on the Canon 50 f/1.4
Canon has issued (September 2017) a Service Advisory for EF 50mm f/1.4 lenses with serial numbers beginning with: “4918”, “5018”, “5118”, “5119”, “5218”, “5219”, “5318”, “5319”, “5418”, or “5419". If you have a lens with such a serial number you may be able to get it repaired by Canon at no charge. For more, please see: Canon Expands Service Advisory for EF 50mm f/1.4 USMs with Focus Malfunction