Please help! 2.5 y/o suddenly eating/biting things..how can I make him stop?

[ginghamgiraffe]

2.5 y/o wasn't really a "mouthy" baby- is a thumb sucker so would be more inclined to do that than suck toys etc when teething - he do

He has recently started biting/eating all sorts of things - cardboard packaging, his nails [ew] the banisters (!), the chalk from his blackboard and yesterday a big lump of playdoh which really upset him cos it obviously tasted grim.
We have repeatedly told him off and asked him why "i don't know."

At a recent appt dentist confirmed all baby teeth are thru, so it's not teething now.

Is it just a phase in which case I need to be repeating the MN mantra this too will pass or is there something constructive I can do to help him stop?? I'm worried he's going to get a chunk of splinter in his gums if he carries on attacking my staircase like this.

TIA

Can you check with the doc that it's not pica? chalk is a classic one for pica. I think its worth getting him checked for iron deficiency just in case. Mine did this, he was slightly low in iron but he was very much a mouthy baby anyway and he did it more when his final molars were coming through.

Thanks owl, had never even heard of pica and have alarmed myself by googling. will check with doc about iron deficiencies.

He does eat an all but veggie diet tbh, not through my choice but through his fussiness so that might not help.

Anyone else have any ideas about prevention methods (other than having eyes installed in the back of my head?!)