Directly, both Meltdown and Spectre won’t really impact your PC any more than a random virus. There are thousands of viruses circulating at any given time, and if you already practice safe computing, you shouldn't be impacted by anything trying to leverage the Meltdown and Spectre vulnerabilities. If you get a virus on your home PC, it's already compromised, and Meltdown and Spectre don't really make the risk any worse.
The main concern revolves around the fix, which is reported to cause a significant slowdown in specific high I/O tasks. Games are generally more GPU bound than they are CPU bound and do not make many or any direct kernel calls at all, so even if the fix impacts you, the performance degradation will likely be small and unnoticeable. Initial benchmarks using Linux and Windows indicate very little change (less than three percent) in performance for common tasks, with data compression (eg, 7-zip) being one of the hardest hit. Gaming benchmarks saw no difference.
The greater risk is for anyone using cloud services. Meltdown as an example is able to read all memory contents on a system from a virtual machine (VM), without breaking any of the security protocols. But unless you’re running a server farm at home, with tenants that might try stealing data from other tenants, you should be fine.