A while ago I received a ticket from one of our customers because User Tracking was not working for NEXUS 5548UP on LMS 3.2. I opened a TAC case for this but this was normal since it is a Datacenter switch. Now the customer came back on this because they really want to see which server is connected to which switch port. I understood from the TAC engineer this is not on the roadmap to integrate in LMS 4.x. They want to know if there exists another product (they thought about DCNM) and wanted to know how this integrates or works together with LMS...
My latest understanding of User Tracking and Nexus 5K series is that it is not supported due to a limitation of the MIB support in the NX-OS.
The current DCNM (release 5.2) is distinct from the LMS and Cisco Prime umbrella but that wil be changing a bit moving forwad as DCNM is enhanced and rolled into the Cisco Prime family. Last I heard there should be some information coming out of Cisco Live this week and a new release will have some additional functionality and better integration. Still, I doubt we'll see UT for the 5K due to the NX-OS limitation.
One way to do what you're asking apart from use of any of the Cisco products is to enable LLDP on your Nexus and servers. That will at least give you the ability to pull the information from the NX-OS command line ("show lldp neighbor")