The same thing happened to me. What I did was epoxy a piece of carbon fibre reinforced end grain balsa between the vertical formers on each side of the inside of the fuselage. these pieces were about 25 mm high, and they spanned the full width from the front former to the rear former. What that did was prevent the fuselage from flexing when the landing gear flexed during landing, which prevents the from delaminating any further.

One additional thing that you might consider doing is making some small holes in the carbon fibre cloth reinforcement on the inside of the fuselage before gluing in the extra pieces so that glue can get into the space behind the gelcoat. (just be very careful not to have the holes go through the gelcoat as well...) Then you can clamp the assembly while the epoxy dries and fix the bulge on the outside.