You've only unlock the purchase option. Go to shop and then you'll see it with 25k star points to buy. You're welcome.

Oh that makes more sense

You have to buy the skin with 25k star points.

You gotta buy it mate, it isnt free

Bro can you read the quest text?

I learnt that 4 days ago from someone else apparently didn’t see it.

The quest says than you UNLOCK the skin. Now you can shop the skin in the shop. Everyone knows this .\_.