lintel above doorway crack

My boyfriend had a man build a concrete block shed over 10 years ago. There was tree in the neighbours garden and after it was chopped down massive cracks apparently started appearing in the wall in that corner, so assumed foundations movement ( concrete base to shed). Last year when I moved in...

There is a crack showing up in the lintel above my front door, most prominent at the bottom but faint line all the way up to a window. Does anyone know how much I would expect a builder to pay to get this fixed? And should I try getting it repaired or just get it replaced? Thank you!