There is nothing at all sexual or inappropriate about the above mentioned gesture. It's a really well known, basic "magic" trick for children. (Making it look like he's removed his thumb and then put it back on again)
Eunice (Fernanda Torres) takes a very thorough shower upon arriving home from twelve days of interrogation and confinement. We see her breasts and buttocks, as does her eleven-year-old son, Marcelo, who walks in on her in the bathroom.