when use past/present tense after said ?

fadi99

When I studied in Secondary School, teacher often told me the tense need to
be consistent in a sentense.

For example, if using \"said\", the rear part of the sentense also need to use
past tense

However, I often see people using present tense after past tense \"said\"

For example,

He said I am a good girl,

he said I am lack of nutrition.

Would you please tell me why the above two sentense use present tense, not
past tense after \"said\"?
When do I use present tense after \"said\" ? When do I use past tense after \"said\"?

Please explain, thx