My 3 yr old pug was in the yard with the other two dogs and he started yelping.?

We went to check on him and nothing seemed wrong. We thought that he may have been sting by a bee or wasp but did not see any locations on his body to indicate this. Now it is night time and he refuses to put his head down, and whimpers and yeps when getting up from a lying position. It is like he is sticking his nose high into the air as if he thinks he might drown. What can I do to help him?