Why did my lip swell ip like a balloon?

Angioedema. Sounds like you have angioedema, which typically presents this way. Try to find what triggered this balloon-like swelling, like foods, blood pressure medications (ace inhibitor), some inhalation or cold exposure, etc. Take h1 and h2 blockers (like Claritin (loratadine) and zantac) while waiting to see a doctor.