Forcefully stopping a sneeze after it has already started, particularly by holding your nose is extremely dangerous — unfortunately you have discovered this the hard way. What you have now ended up with is a ear infection, but hopefully no permanent damage.
During a sneeze your body expels air at a tremendous speed. After the process has already begun, trying to stop it by blocking the sneeze is extremely dangerous — the air has to go somewhere, and it gets forced into your ear passages, which, as you know are connected to the nasal passages. The built up pressure can damage both passages and the sinuses, and also forces bacteria into these areas, turning your nasal infection into a ear infection or a sinus infection as well. In severe cases, it is also possible to rupture the ear drum by stifling a sneeze.
You should visit a doctor as soon as possible, preferably a ear specialist, and find out whether there is any damage, and what needs to be done to treat it. In future, let yourself sneeze heartily — a little noise will not hurt anyone, and the sneeze will also get rid of whatever is irritating your nose. Simply cover your nose and mouth, sneeze, and excuse yourself.
answered by M W