A gap between the edge of a built-in cabin and the wall can stick out like a sore thumb. Since you can't readjust the cabinets themselves, you will need to find another way to close the gaps and give the cabinets a polished, complete look. Rather than call a professional and spend excess money on the project, you can purchase a few simple supplies from any hardware store and take care of the problem yourself.
Measure the length of the gap in between the built-in cabinets and the wall with a measuring tape.
Cut a length of foam backer rod using a pair of scissors to match the measurements you took of the gap.
Stuff the foam backer rod about 1/8 of an inch into the gap with a putty knife.
Apply a line of caulk over the stuffed gap.
Dip your finger into water and run it over the freshly applied caulk to smooth the surface. Allow the caulk to dry completely.
Paint the caulk in a shade that matches your wall exactly.