git still shows files as modified after adding to .gitignore

i’m adding this to .gitignore file

.idea/*

but anyway the status is:

#       modified:   .gitignore
#       modified:   .idea/.generators
#       modified:   .idea/dovezu.iml
#       modified:   .idea/misc.xml
#       modified:   .idea/workspace.xml

what am i doing wrong ?
i even added .idea/* to the global ~/.gitignore_global
but git status, anyway shows me:

#       modified:   .gitignore
#       modified:   .idea/.generators
#       modified:   .idea/dovezu.iml
#       modified:   .idea/misc.xml
#       modified:   .idea/workspace.xml