Diary - My mum showed

[Maybo]

This is an entry from my diary. Please check it and correct any mistakes.

My mum showed me her wrist a few days ago. She said she'd felt that her skin near her wrist puffed. I looked at it, and it did puffed a bit. I pressed it but felt nothing strange in it. Today, she saw a doctor, and he told her that it was just fat. When I heard that, I laughed at her and said she'd just gained weight.

 

[emsr2d2]

"Puff" is a verb so you can't say "did puffed". It's more natural to use the associated adjective "puffy". Try to rewrite your piece with that in mind.

 

[Maybo]

Revised:
My mum showed me her wrist a few days ago. She said she'd felt that her skin near her wrist was puffy. I looked at it, and it did look puffy a bit. I pressed it but felt nothing strange in it. Today, she saw a doctor, and he told her that it was just fat. When I heard that, I laughed at her and said she'd just gained weight.

 

[emsr2d2]

Revised:
My mum showed me her wrist a few days ago. She A few days ago, my mum said she'd [that] she felt that her the skin near her wrist was puffy. I looked at it, and it did look puffy a bit puffy. I pressed it but felt nothing strange. in it. Today, she saw a doctor, and he told her that it was just fat. When I heard that, I laughed at her and said she'd just gained weight.

See above. Starting with the fact that she showed you her wrist meant that "I looked at it" became redundant. It makes more sense to open with what she said she felt and follow it by saying you had a look.
I suggested "puffy" because it fitted with your original "puff". However, I would use "swollen" both times.
It's not very nice to say that you laughed "at her". That suggests you were mocking her for being worried, which isn't very kind of you. Just saying you laughed is enough.