Respond for Apologies & Thanks

[Azaboy]

Konichiwa
I was in Tokyo Disneysea last year for my summer yasumi. Was walking when a small boy bumped into me accidentally. He said gomendasai, paused and ran away with a frantic look thinking I was angry or something. But truth is, I was stunned cos I dunno how to say 'It's ok' or 'it's alright' in japanese. Can somebody help me? N what's the reply for 'my pleasure' or 'don't mention it' after someone say thank you to u?
p.s. still learning kanji so romaji wud be good

[jemstone]

だいじょうぶ [大丈夫] (da-i-jo-u-bu) would be a good respond to the little boy's "gomennasai". it roughly translates to "it's ok." or "i'm ok."

as for a response for "thank you", could use どういたしまして (do-u-i-ta-shi-ma-shi-te, i'm not quite sure if there's a small tsu between い and た). I think there's a shorter version of this. roughly translates to "you're welcome."

[Javizy]

I think these phrases would work okay. You can start them with iie/iya/iyaiyaiya. You can also speak casually to kids if you like.

Nan demo arimasen.
It's nothing.
Ki ni shinakute mo ii n desu / Ki ni shinai de kudasai.
Don't worry about it.
Ayamaru koto wa nai n desu.
There's no need to apologise.

[Azaboy]

Domo arigato gozaimasu!