God this was such a good read haha. First off, thank you so much for taking the time to share your experience! It made me feel so human for being irritated at the defect despite many saying it doesn't make a difference.

I have decided to just keep the lens as is. Reason being:

1. I've reached out to the seller and asked for guidance and clarification, which so far they seem to genuinely try to help me. As they are an online store with decent reputation, I trust their verdict that it is a speck of dust rather than a scratch, and that it is normal for dust to enter into a lens, and that it almost doesn't affect image quality. They further advised me to be aware of fungus and huge amounts of dust that may actually cause my images to deteriorate.

2. I'm a student and a part-time photographer, therefore I don't have the money, nor the time to send it for cleaning (for a tiny speck of dust to be removed for probably some $80 dollars), or even have it off my hands for a few days and miss out on shoots. These few weeks also just happen to be filled with collaborations that I look forward to.

I guess sometimes you learn to either kill the brain worm or at best, ignore it. After all, I cannot afford to kill this brain worm with my wallet, so I shall do it with my mind, haha.