My daughter had that for a few days when she was a couple of months old. What I did was to use a cotton ball and sterile water and swab it every hour or so, just one straight wipe across her eye to remove the wax. It cleared up after that and she has not had it since. Sometimes it can happen if the child has an underlying illness like a cold or an ear infection so I would just keep monitoring it an if it does not clear up then take her to the doctor. I would check her ears to see if she has excess wax there too, as my daughter did and the doctor ended up having to remove it as it was getting hard inside her ear.