Greenhorn
/ˈɡriːnhɔːrn/
Definition 1 of 2
Pro Tip 1/3Learning Curve
Greenhorn implies someone is at the beginning of learning something, with much to learn. 
Don't be harsh on yourself for the mistakes, every greenhorn goes through this.
Pro Tip 2/3Colloquial Usage
The word 'greenhorn' is casual and may not suit formal or business situations. 
At the start-up, we all were greenhorns cracking jokes at meetings.
Pro Tip 3/3Not Negative
'Greenhorn' isn't necessarily an insult, it can simply state a fact. 
It's not bad being a greenhorn, as everyone starts somewhere.