Not much to see
Milan, other than the cathedral and high-end shopping (if you are interested), doesn't have much to offer. You can add the San Siro football stadium but I went in the off-season. A day trip to Lake Como is worthwhile though (I was a little unlucky that the funicular in Como town was closed for maintenance and I missed the fast ferry).
Insider Tip:1. Steps leading to top of Milan Cathedral open at about 9 am - definitely worth a visit
2. If you are planning a day trip to lake Como, take the morning train to Varenna (one of many towns on the lake), short ferry to Bellagio and the longer ferry to Como town from where there are hourly trains back to Milan. Trains to Varenna from Milan are infrequent - check timings in advance