Both sentences are correct. For you first sentence, you could also say:
1. Sorry, I'm not that great at English.
2. Sorry, I'm not fluent in English.
3. Sorry, my English sucks. (Informal/Somewhat vulgar)
4. Sorry, I suck at English. (Informal/Somewhat vulgar)
5. Sorry, English was never my strong suit.
6. Sorry, I can't speak English well.
7. Sorry, I'm not proficient in English.