Oil fire central heating - ? blown fuses?

[Ula NI]

Bear with me., this is heating related: All sockets tripped -Thought it was caused by an old coffee appliance my husband was cleaning out.
We checked the fuse board and the RCD wouldn't reset - unplugged everything, then reset it - sockets back.

The heating system/burner had no life. Husband replaced the fuse in the meter board, then it fired up.
Think the LED light is gone on the facia plate (A in photo) - is this something to worry about?

In the meantime, I've noticed a leak at the side of the burner - see photos
Our burner/pressurised water tank is inside our house (off the back kitchen, house built 19 years ago)

what could be the cause of the leak? Its dripping rightly.
We'll try to get hold of our boiler servicer in the morning - anything i can do now to stop that leak?

 

[Exedon]

Leak could easily be the auto air valve above the steel tee
Carefully try tighten red cap on top down

 

[Ula NI]

Thank you for responding. We have our boiler guy coming first thing so he can replace it or fix it....it's not dripping as much at the min.