Hi! I'm not a fresh grad but just wanted to share that my undergrad degree isn't related to public policy. My work experience isn't even explicitly related to my undergrad degree... I probably just used about 10-20% of what I learned in school ? (thanks to globalization).
Point is, I think if you're able to connect and explain thoroughly your decision/motivation in pursuing public policy (and why choose it instead of all the other "more" relevant fields), I think you'll be okay. Show them (through your SOP) that your interest in public policy is real :)