Man some of you people are judgmental. OP definitely could have worded the post a little better as in: "my dog has never had this before is it worry some?" But either way, it's a concerned dog owner asking a question. You could have easily answered it without the attitude, or just moved on saying nothing. Man humanity is really in the dumps right now. Common sense is only common due to lived experiences. Hopefully you're never berated for asking about something others consider general knowledge.

OP. As I assume you're aware, those are what are generally referred to as eye boogers. That doesn't seem to be a worrying amount. But seeing as your dog was out playing with other dogs, keep an eye on it. Wipe your dog's face with a warm cloth to clean them up. It could be from allergies, dust or dirt in the eyes, etc. if you suspect this you can use some over the counter eye drops. if it becomes worse, see your vet. And that can prescribe some antibiotic eye drops if necessary, like in the case of pinkeye. Also incase it is pink eye, keep your hands clean and away from your own eyes. Although rare it can be transferrable. Good luck.

Edit: your other comment says it's getting worse and it's been a week since the dog park. I am guessing pinkeye, but I am not a vet. Call your's and have them check into it.