I really need my child to have a good day

[pgcountywoman]

My Son is 21 months old.  He attend daycare while I work.  The problem is lately I have been getting complains about him showing aggression towards other children.  When I dropped him off today, I witnessed him hitting a child and pushing another child down.  Last week, I had a meeting with the director of the daycare because they stated that a parent complained about how aggressive my Son was with another child in the classroom.  I've been extremely stressed out.  Because of his age, and limited language abilities, I try to remind him that he should use, "gentle touches", or when he does something wrong, I say, "not nice."  I have googled appropriate behavior for toddlers his age and I don't see anything out of the ordinary.  However, I don't want my Son to hurt other children and on the other hand, I don't want him labeled.  And on his daily progress report for day, I learned that he hit the Teacher.  What do I do?.  Whatever advice someone can help me with will be appreciated.