Congrats on the goal, nicely done! Haven't played footy myself since last Sept, I miss it.
I would make sure to supplement with Magnesium pills. Magnesium citrate seems to be the most common version of supplement on the shelves where ever I look.
M. Citrate can have an effect in your stomach, so don't over do its intake... (as in, runny tummy.)
I get calf cramps, and a tight neck from keyboarding, so I take about 300 mg of Mag. Citrate a day: that's one 150 mg pill, between meals, twice daily.
Like others recommend I also take an Epson salt bath before going to bed, helps a lot.
When I played a lot and sometimes semi-pulled a quad muscle I was advised to stretch them gently while applying ice (place ice pack on quad and stretch VERY gently). Of course use ice sparingly too, as not to restrict blod flow to the area for too long. Everything in moderation...!
After training/games, make sure to stretch well. I would sit on floor at home, stretching while watching tv...
Elevate the poorly knee and apply ice pack (bag of peas, whatever) for 10 minutes to lessen any potential swelling.
Also make sure to drink lots of water, this will help muscles "regenerate" after exercise. It's actually very important to also hydrate well BEFORE exercise, so drink plenty of water 2-3 hours before a game/practise.
What position do you play? I was always centre mid, and loved it