Dental retainer problem pls help?

So I got my braces removed last week, they gave me an essix retainer and said the gum would "tighten up" and it's normal to bleed. There are gaps between my molars after removing the braces, not too big, just big enought for a little piece of food to get stuck in them. Brushing doesnt work, dental floss is ineffective because there's a gap, so I decided to use toothpick. One night a lot of blood came out. I thought I accidentally poked too hard or something. I waited for the bleeding to stop thsn wear my retainer and sleep. Few days later (now), there's a particularly red spot in that place. I tried touching it gently and found out it is like detached from the molar. The size of the red gum is very small, almost like a little triange at the gap area. Is the retainer preventing it to heal? Why is it detached? What is happening?
Please help me