Wobbly plaster/ Mortor behind my window trim

[Idiyh]

Where the wall meets the window there is a plastic trim. I took it off because there is a damp patch under the window sill in the corner. I was trying to find the answer to the damp and so took the plastic trim off. It's about an inch thick. This brought off some of the skimmer plaster but behind it there is plaster/Mortor that is cracked but stuck there wobbling... What is the best way to repair it. For the gap I was gunna foam it but I cant just leave broken bits of plaster/Mortor holding on. Can you help me please.... It has been causing me alot of stress

 

[dontbelieveawordofit]

picture.

 

[Idiyh]

I'm having so much trouble adding a photo.... I will try

 

[Idiyh]

hi this is the picture...thankyou . I really hope you can help I would very much appreciate it

 

[Idiyh]

its this area that is wobbly, loose and thick, but also cracked

 

[dontbelieveawordofit]

the highlighted piece is loose?

 

[Idiyh]

That's right it is. What would you recommend to do to fix it?
Thankyou

 

[Tigercubrider]

Can you pullit out?
You'd probably be able to "glue" it back in with some filler/plaster then skim over.

If not, break it up and remove, buy a small bag of rapid set cement and fill it.
Give it 24 hrs to dry