Air escapes from the valve area if it's slightly misaligned or needs tightening up. This a common issue but isn't anything to be concerned about. It's super easy to sort out as part of your regular SUP maintenance regime, simply follow the steps below:
Retrieve your SUP repair kit from your bag and locate the valve tool.
Remove the valve dust cap and loosen the valve using the valve tool.
Fully unscrew and remove the valve.
Check the O ring is in place and that the spring on the pin is functioning.
Check the valve thread for any other obstructions.
Screw the valve back into your SUP hand tight, and then finish with the valve.