Nikki Bella Steps Out with Son After Filing For Divorce From Artem Chigvintsev

Nikki Bella isn't just a former WWE Superstar ... she's a super-mom too -- spending some quality time with her four-year-old Matteo after filing for divorce.

The former wrestler stepped out in Napa Valley Friday ... taking her son to his dance class with a big smile on her face.

Check out the pics ... both Nikki and her son look ready to work out -- twinning in all-black, sporty outfits.

Nikki definitely participated in some self-care Friday afternoon ... grabbing a couple green health drinks to cool off in the hot California sun -- once again without her ring, no less.

Nikki's outing came just a few days after she officially filed for divorce from Artem Chigvintsev ... bringing an end to a two-week-long saga that kicked off after AC's arrest for felony domestic violence.

As we told you ... Artem called the paramedics to request medical assistance for the alleged victim before calling them off just minutes later. Police officers showed up anyway -- per standard operating procedure -- and arrested Chigvintsev.

Nikki stopped wearing her wedding ring almost immediately after the arrest ... and, just before she filed, we broke the story that she was shopping for divorce lawyers.

NB asked for legal and physical custody of their son in her divorce filing ... while also checking the box saying she's open to Artem having visitation rights.