it's impossible for me to say what exactly is to blame for the increased sensitivity of your clitoris which you noticed.
Like you wondered, slight chafing from your pad might be to blame, it could be the time of your cycle, too. - Many women notice that they are more aroused and more easily stimulated (or have more sensitive genitals) at certain points in their cycles.
Regarding the scratch: scratches on your gentials can easily happen, for example through rough masturbation or manual sex without sufficient lubrication, or through jewellery when changing your pad or tampon.
In any way, I wouldn't stress at all right now about either, and instead take a wait and see approach.
If you find you're still concerend about what's going on with yoru genitals in a few days, going to a doc can of course never harm.
Also, if you're sexually active and worrying about STDs, I wholeheartedly recommend getting regular screens and practising Dafer Sex.
Spike: Well, I'm not good and I'm okay.