The past tense of ‘sew’ is ‘sewed’. For example, ‘Yesterday, I sewed a button on my shirt.’ However, the past participle form is ‘sewn’. So, you might also say, ‘I have sewn many dresses in my life.’ Both forms are correct, but they are used in different contexts. ‘Sewed’ is used for simple past tense, while ‘sewn’ is used with helping verbs like ‘have’ or ‘has’.