"Sorry for interrupting". No other form of the verb is possible.
Here's an important rule for you:
Prepositions - e.g. for, of, from, by, on, with, at, from - should always be following by the -ing form. You can never have a base form or conjugated past or present tense of a verb after these words.
(The only exception to this rule is the preposition 'to', which is often (but not always) followed by the infinitive).