What do I do about a forgotten, ancient PGP key?

So I just created a new PGP key because I want to start using PGP to encrypt my emails. Lo and behold, this is apparently not my first attempt to use PGP. Five years ago, I created another PGP key using an ancient encryption algorithm (DSA 1024-bit). This would be very easy to crack.

Needless to say, I don't have a revoke certificate for it. What should I do?